Battery replacement determination method for series hybrid system, battery replacement determination device, and recording medium

Abstract

In order to provide a deterioration index of a battery for calculating and presenting degradation of fuel consumption due to deterioration of the battery and determining the appropriateness of replacement of the battery, the present invention proposes a battery replacement determination method for a series hybrid system, the method involving, in the series hybrid system, calculating and outputting fuel consumption in the case where the battery is replaced, on the basis of the capacity deterioration ratio and the resistance deterioration ratio of the battery and of on / off information regarding an engine or a fuel cell (see fig. 1).

Description

Battery replacement determination method for series hybrid system, battery replacement determination device and recording medium

[0001] The present invention relates to a battery replacement determination method, a battery replacement determination device, and a recording medium for a series hybrid system, for example, one that uses a lithium ion battery.

[0002] A mobile body equipped with a series hybrid system (for example, a series hybrid vehicle) supplies electricity generated by an engine or other device to a battery and a motor, and the battery compensates for load fluctuations on the motor, thereby maintaining a constant load on the engine and improving fuel efficiency. Hereinafter, a series hybrid system or a mobile body equipped with such a system may be simply referred to as a "series hybrid."

[0003] Generally, as a battery ages, its Ah capacity decreases and its resistance increases, making it difficult for the battery to compensate for fluctuations in motor load, resulting in a deterioration in fuel efficiency and the need to replace the battery.

[0004] Batteries used in series hybrids include lithium-ion batteries, lead, NiH, and solid-state batteries. Conventional battery replacement indicators include SOHR, which indicates how many times the battery resistance has increased compared to its initial state when converted to a specific temperature (e.g., 25°C), SOHQ, which indicates how many times the Ah capacity has increased compared to its initial state, and Wh capacity, which indicates mileage, compared to its initial state. However, none of these indicators directly indicate fuel economy.

[0005] A method for indicating the degree to which fuel economy has deteriorated due to battery degradation is described, for example, in Patent Document 1. Specifically, the method describes a method of conducting fuel economy tests in advance using several driving patterns to create a database, and then calculating the deterioration in fuel economy by comparing the current fuel economy with the results of a fuel economy test that is closest to the current driving pattern.

[0006] Japanese Patent Application Laid-Open No. 2007-274806

[0007] However, fuel economy is affected not only by battery degradation, but also by the driver's specific driving patterns and the degradation of the engine, etc. Therefore, the present invention aims to provide a battery degradation index that calculates and displays the deterioration of fuel economy due to battery degradation and allows a user to determine whether or not to replace the battery.

[0008] One example of a method for determining battery replacement in a series hybrid system according to the present invention calculates and outputs fuel efficiency in the event of battery replacement in a series hybrid system based on the battery resistance deterioration factor, capacity deterioration factor, and engine on / off information.

[0009] One example of a method for determining battery replacement in a series hybrid system according to the present invention involves, after the series hybrid system has been operated, replacing the current battery with another battery to change the SOHR and SOHQ. The method calculates the current and voltage of the other battery based on the voltage and temperature of the current battery, a time series of the current battery, the load current, the load voltage, a time series of fuel consumption, and on / off information of the engine or fuel cell of the series hybrid system. When calculating the current and voltage of the other battery, it is assumed that the power of the load, given by multiplying the load current by its voltage, remains unchanged. The engine or fuel cell is turned on when the battery reaches a predetermined lower limit of SOC or minimum stored energy, and turned off when the battery reaches a predetermined upper limit of SOC or maximum stored energy. The SOC of the battery is updated based on the current and voltage of the other battery, and the on / off time series of the engine or fuel cell is calculated. Fuel consumption is calculated based on the on / off time series of the engine or fuel cell, the fuel consumption when the engine or fuel cell is on, and the extra fuel blown when the engine or fuel cell is turned on.

[0010] An example of the battery replacement determination device for a series hybrid system according to the present invention executes the above-described method.

[0011] An example of a recording medium according to the present invention is a recording medium on which a program for causing a computer to execute the above-described method is recorded.

[0012] The present invention eliminates the influence of driving patterns and engine or fuel cell deterioration, and provides only the deterioration in fuel economy due to battery deterioration, thereby making it possible to determine whether battery replacement is necessary.

[0013] Problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments.

[0014] FIG. 1 is a series hybrid configuration diagram. FIG. 2 is a diagram showing the principle of fuel efficiency calculation. FIG. 3 is a diagram showing an example of an OCV-SOC relationship table. FIG. 4 is a diagram showing an example of a screen. FIG. 5 is a diagram showing an example of a fuel efficiency calculation flow when the battery is replaced with a new one after one trip. FIG. 6 is a diagram showing an example of a battery circuit model. FIG. 7 is a diagram showing another example of a fuel efficiency calculation flow when the battery is replaced with a new one after one trip. FIG. 8 is a diagram showing an example of a multiplication factor based on resistor temperature. FIG. 9 is a diagram showing server cooperation. FIG. 10 is a diagram showing an example of a predicted cost.

[0015] Hereinafter, an embodiment of the battery replacement determination for a series hybrid vehicle according to the present invention will be described with reference to the drawings. Note that the same components in each drawing are designated by the same reference numerals, and detailed descriptions of overlapping parts will be omitted.

[0016] [Example 1] Fig. 1 is a diagram showing a schematic configuration example of a series hybrid. The configuration in Fig. 1 is realized using software, and is processed by an embedded computer in the series hybrid or a server via communication.

[0017] The series hybrid includes an ECU 101 (engine (hereinafter referred to as "engine or fuel cell") control unit). The ECU 101 has a hardware configuration as a computer, and includes, for example, a calculation means and a storage means. The calculation means includes, for example, a processor, and the storage means includes, for example, a storage medium such as a semiconductor memory device. Some or all of the storage medium may be non-transitory storage media.

[0018] The computer may also include input / output means, which may include a communication device such as a network interface.

[0019] The storage means may store a program. The processor may execute the program, causing the computer to function as the ECU 101 described in this embodiment. In other words, the program causes the computer to execute the battery replacement determination method described in this specification.

[0020] The series hybrid can function as a battery replacement determination device for a series hybrid, that is, can execute the battery replacement determination method for a series hybrid described in this specification.

[0021] In the series hybrid system, on / off information for the engine (hereinafter referred to as "engine or fuel cell") is obtained from ECU 101 via the LAN within the series hybrid system, and resistance information and battery SOHQ (the percentage of the current battery's Ah capacity relative to the Ah capacity of a new battery) information are obtained from BMU 102 (battery management unit) via the LAN within the series hybrid system.

[0022] In addition, the amount of extra fuel (unit: g or L) blown when the engine is on and the amount of fuel consumed (unit: g / s or L / s, g / h, L / h) blown at a constant rate when the engine is on can be obtained from the ECU, and if this value cannot be obtained, the value can be stored as a predetermined specified value.

[0023] Next, the fuel efficiency conversion unit 103 calculates and outputs the time-averaged fuel efficiency (g / s or L / s, g / h, L / h, g / kWh, L / kWh) if use is continued without replacing the battery (and therefore without changing the current on / off cycle) using the above-mentioned values, and the time-averaged fuel efficiency if the battery is replaced with a new one.

[0024] The fuel consumption conversion section will be described later, but calculations may also be performed on the server.

[0025] Here, the fuel efficiency may be output as a fuel consumption rate ratio when the battery is replaced with a new one (details will be described later; the fuel efficiency (g / s or L / s) when the battery is replaced with a new one divided by the current fuel efficiency (g / s, L / s, g / kWh or L / kWh) or as a percentage). Note that in this specification, "current state" may refer to the state before the battery is replaced.

[0026] The series hybrid also contains an engine 104, a generator 105, a battery pack 106, a drive motor 107, and a hydraulic motor 108 (there are other loads as well, but these are not shown), and the generator 105, the battery pack 106, the drive motor 107, and the hydraulic motor 108 are connected by power lines.

[0027] The generator starts generating electricity at a constant speed when the battery pack's State of Charge (hereinafter sometimes referred to as "SOC") falls below a predetermined lower limit SOCL, supplying energy to the battery pack and motor. When the battery pack's SOC rises above a predetermined upper limit SOCH, it stops generating electricity. When the generator is not generating electricity, the energy for each motor is supplied from the battery pack.

[0028] Next, the details of fuel efficiency calculation will be explained using Figure 2. In Figure 2, the horizontal axis is time and the vertical axis is fuel efficiency (here, L / s). When the engine is turned on, the extra fuel μ (L) required to turn the engine on is blown, and thereafter a constant fuel f (L / s) is blown.

[0029] A series hybrid operates the engine at the optimum fuel efficiency point. Generally, the load on a series hybrid fluctuates, but the fluctuations are absorbed by the battery. Apart from automobiles, agricultural and construction machinery undergo routine tasks, so the engine on / off cycle is almost constant (railroads will be discussed in Example 2). The current fuel efficiency is f × engine on time + μ [L] of fuel consumed in one cycle. Therefore, the fuel efficiency in one cycle is (f × engine on time + μ) / cycle T [L / s].

[0030] Next, we will calculate the fuel efficiency when the battery is replaced with a new one. The energy required in one cycle, converted into fuel, is f × engine-on time + μ. However, when the battery is charged or discharged, energy is lost due to resistance in the battery. As a result, the engine-on time will be extended by 1 / ηc times the input energy, and the engine-off time will be ηd times (ηc is the charging efficiency of the battery's stored energy / charging input energy, and ηd is similarly the discharge energy / battery's stored energy). For this reason, we will explain how to calculate ηc and ηd.

[0031] When the battery is being charged with the engine on, energy is supplied directly to the load from the generator. The charging efficiency ηc at this time is defined as Equation 1: ηc = Et / Ec ... (Equation 1) To calculate ηc, first find the current input energy Ec by integrating V x I during charging with the engine off. I is the battery current, with the charging side being positive. Then, find the OCV separately and calculate the energy stored in the battery as Et = ∫OCV(SOC(t)) x I・dt. The method for calculating OCV will be described later. The engine-on time is assumed to be when the battery is new.

[0032] Here, when the battery is replaced with a new one, the battery resistance will be multiplied by SOHR_after / SOHR_present. SOHR_after is the SOHR after replacement, set to 100 here. SOHR_present is the current SOHR. Therefore, the input power to the battery is (OCV + (V-OCV) x SOHR_after / SOHR_present) x current I when charging. This is because when charging, "current V" > OCV, and (current V-OCV) / I becomes the resistance.

[0033] Now, if x = SOHR_after / SOHR_present, ηc is expressed as Equation 2. ηc(x) = Et / {Ec*x+Et*(1-x)} ... (Equation 2)

[0034] Similarly, the discharge efficiency ηd can be defined as Equation 3. Here, Ed is the integral of V×I during discharge while the engine is off, over the engine-off time period. ηd(x) = {Ed*x+Et*(1-x)} / Et ... (Equation 3) Note that Ed and Ec are calculated under the assumption that there is no regeneration of the battery during engine-off time and no discharge of the battery during engine-on time. If this is not the case, Ec is defined as the integral of the period during which the battery is charging, and Ed is defined as the integral of the period during which the battery is discharging. This is because the calculation of charging and discharging efficiency is based solely on the period during which the battery is discharging or charging. Time periods during which there is no charging or discharging can be excluded (note that even if these are not excluded and totaled as either the charging or discharging side, the results will not be affected because the current is zero).

[0035] Next, we define the charge / discharge efficiency as η(x) = ηc(x) × ηd(x). When a battery is new, the charge / discharge efficiency is approximately 95%.

[0036] In addition, the integral time of the SOHQ (a percentage calculated as the current Ah capacity / Ah capacity when new) changes when the battery is replaced with a new one, i.e., the cycle changes. This is because the engine is on during the period when the SOC goes from SOCL (e.g., 20%) to SOCH (e.g., 80%), so the cycle is basically proportional to the SOHQ.

[0037] The cycle T when the battery is replaced with a new one is T × SOHQ_after / SOHQ_present (where SOHQ_after = 100). Therefore, the engine off time Y after replacing the battery with a new one is given by Equation 4. This is because Y is proportional to ηd. In this way, the deterioration of charging efficiency can be determined based on SOHR, and the engine on time can be extended. Y_after = Y × (ηd_after / ηd_present) × SOHQ_after / SOHQ_present = {Y × ηd(100 / SOHR) / ηd(1)} × {100 / SOHQ} ... (Equation 4)

[0038] Here, ηc(1) is [current charging voltage x I integrated over the charging period] / Et. The engine on time X after replacing the battery is calculated as Equation 5. This is because X is proportional to 1 / ηc. In this way, the deterioration of discharge efficiency can be determined based on SOHR, and the engine off time can be shortened. X_after={X×ηc_present / ηc_after}×(100 / SOHQ)={X×ηc(1) / ηc(100 / SOHR)}×{100 / SOHQ} ... (Equation 5)

[0039] As a result, the fuel consumption when switching to a new battery is calculated as in Equation 6. F_after[L / s] = (η × engine on time + μ) / cycle T = [f × {X × ηc(1) / ηc(100 / SOHR)} × {100 / SOHQ} + μ] / [{X × ηc(1) / ηc(100 / SOHR)} × {100 / SOHQ} + {Y × ηc(100 / SOHR) / ηc(1)} × {100 / SOHQ}] = {f × X + μ × (SOHQ / 100) × ηc(100 / SOHR) / ηc(1)} / {X + Y × η(100 / SOHR) / η(1)} … (Equation 6)

[0040] Equation 4 applies when the current SOHR and SOHQ are replaced with new batteries, but if the battery's SOHR and SOHQ virtually change from SOHR_present and SOHQ_present to SOHR_after and SOHQ_after, the equation becomes Equation 7. Here, x = SOHR_after / SOHR_present, y = SOHQ_present / SOHQ_after. F_after(x, y) = {f×X+μ×y×ηc(x) / ηc(1)} / {X + Y×η(x) / η(1)} ... (Equation 7)

[0041] If we first determine η, μ, X, and Y assuming a new battery, and then the battery deteriorates from that state so that SOHQ and SOHR become SOHQ1 and SOHR1, respectively, then F_after={f×X+μ×(100 / SOHQ1)×ηc(SOHR1 / 100) / ηc(1)} / {X + Y×η(SOHR1 / 100) / η(1)}, where η(1) is the charge / discharge efficiency when the battery is new.

[0042] The fuel economy shown in Equation 4 and Equation 5 reflects the driving conditions. Furthermore, if η and μ are obtained via communication, they will also reflect engine deterioration. The above is an example in which SOC can be obtained from the BMU and a table of the relationship between OCV and SOC is stored in the fuel economy conversion unit. An example of this OCV and SOC relationship table is shown in Figure 3. OCV is calculated from SOC based on this table.

[0043] If there is no relationship table between OCV and SOC, or if SOC information cannot be obtained, it is necessary to estimate the loss rate. In this case, η_after can be approximated using Equation 8. η_present is Ed / Ec. If the current SOHR is SOHR2 and it is to be replaced with a new one (SOHR=100), it can be approximated as η_after=1-(1-η_present)*100 / SOHR2. ηc_after can also be calculated using the same formula as Equation 8. η_after ≒ 1-(1-η_present)×SOHR_after / SOHR_present … (Equation 8)

[0044] The graph in Figure 3 is an example showing the relationship between OCV and SOC, but as shown on the vertical axis, resistance can be used instead of OCV. In that case, a table showing the relationship between resistance and SOC can be used. In this case, the specific content (graph) of the relationship table will differ from that shown in Figure 3, but the processing can be performed in the same way.

[0045] Next, we will discuss examples of displays for users (e.g., administrators, drivers, or vehicle owners). It is possible to display the current fuel economy, the fuel required when a new battery is installed, SOHF (State of Health based on Fuel, the rate of fuel economy deterioration due to battery degradation), etc. It is also possible to display information about the cost change over time if the battery is continued to be used as is, and the cost change over time if the battery is replaced now. The cost is the sum of the accumulated fuel cost and the cost of battery replacement. The cost of battery replacement includes, for example, the selling price of the battery and the handling fee for the replacement work.

[0046] An example of this display is shown in Figure 4. This screen may be displayed on a display device (panel, etc.) mounted on the series hybrid, or may be viewed on a remote computer using a browser, etc.

[0047] The display example in FIG. 4 shows the current fuel efficiency 41 (here, L / h), the fuel efficiency 42 (here, L / h) when the battery is replaced with a new one, the rate of fuel efficiency deterioration due to battery degradation 43 (SOHF), a time series of SOHF 44, and a time series of total cost 45 (including at least the integrated value of fuel cost and the cost of battery replacement).

[0048] SOHF (State of Health based on Fuel) is a percentage of "current fuel economy / fuel economy when the battery is replaced with a new one" and is defined as Equation 9. The SOHF displayed here is SOHR_after = SOHQ_present = 100, where SOH_present is the current SOH, and SOHQ_before is the current SOHQ. SOHF = 100 × F_after (SOHR_after / SOHR_before, SOHQ_before / SOHQ_after) / F_after(1,1)... (Equation 9)

[0049] Here, the unit of fuel efficiency is L / h, but it may be kg / h, L / kWh, kg / kWh, L / operation, or kg / operation, or the value may be displayed in all units, or any unit may be selectable. L / operation and kg / operation will be described in Example 2.

[0050] For example, as shown in FIG. 4 , the series hybrid according to the first embodiment can display fuel efficiency in at least one of the following units: - "volume of fuel consumed / hour", - "volume of fuel consumed / energy used by the series hybrid system", - "volume of fuel consumed / energy used in one operation", - "mass of fuel consumed / hour", - "mass of fuel consumed / energy used by the series hybrid system", - "mass of fuel consumed / energy used in one operation".

[0051] This allows the user to select the desired unit, improving convenience.

[0052] If the fuel consumption information from the ECU is in g / s, the weight of fuel used can be calculated by time integration, but if it is in L / s, kg can be calculated by dividing by the specific gravity of the fuel (for example, diesel). Here, calculation of L / kWh is possible if the current Ig generated by the generator can be measured and this information can be obtained from the ECU.

[0053] The current of the load (hydraulic motor, etc.) is Ig-I (I is the battery current, with the charging side being positive). In other words, the power consumed by the load is the battery voltage V x (Ig-I), and the value E obtained by integrating this value over one cycle is the energy consumed by the load. The fuel consumption unit L / kWh is the value obtained by dividing the fuel L used in one cycle by E. When this unit L / kWh is used, the efficiency of the motor is constant regardless of the rotation speed or torque, so it is a fuel consumption index that is not easily affected by operating conditions.

[0054] The SOHF display may be the current calculated value (value for the current temperature), or may be a value converted to a predetermined temperature (for example, 25°C), or if necessary, may be a value converted to the predicted or actual minimum temperature for the day. These temperature-specific displays may also be displayed together. A specific method for temperature conversion will be described in Example 3.

[0055] Next, the time series of SOHF may display the recorded SOHF calculated from past operations, or may be calculated by converting it to a predetermined temperature (for example, 25°C), or both time series may be displayed. This conversion method will be described in Example 3.

[0056] In this way, the series hybrid according to Example 1 displays the SOHF (State of Health for Fuel consumption), which is an index of the impact of battery degradation on fuel economy, as the ratio between the current fuel economy and the fuel economy that would be achieved if the battery were replaced with a new battery.

[0057] This allows the user to easily understand the comparison results.

[0058] The series hybrid according to the first embodiment also presents a time series and a predicted value of the total cost, where the total cost includes at least the integrated value of the fuel cost when the battery is replaced and the battery replacement cost.

[0059] Therefore, the total cost can be calculated by appropriately taking into account various costs.

[0060] Next, we will explain how to calculate fuel efficiency when the battery discharges while the engine is on and when regeneration occurs while the engine is off. If the time when the battery discharges while the engine is on is Td [hours], this will be a fixed time. Therefore, the engine on time is calculated by multiplying (X-Td) by ηc(1) / (ηc(x)×y) and adding Td to the result.

[0061] Similarly, for regeneration while the engine is off, multiply (Y-Tc) by {Y×ηd(x)} / (ηd(1)×y). Add Tc to this. Tc is the regeneration time while the engine is off.

[0062] Then, substitute this into Equation 6 to estimate the fuel economy after the battery replacement, where x = SOHR_after / SOHR_present, and y = SOHQ_present / SOHQ_after.

[0063] As shown in FIG. 1, the series hybrid according to the first embodiment determines the engine on / off cycle in proportion to the SOHQ. Then, the deterioration of charging efficiency is determined based on the SOHR, and the engine on time is extended. Furthermore, the deterioration of discharging efficiency is determined based on the SOHR, and the engine off time is shortened. The fuel economy is calculated based on these. Therefore, the deterioration can be more appropriately considered.

[0064] Next, we will explain the total cost time series 45. The total cost time series 45 plots the number of years since purchase of the series hybrid (years of use) on the horizontal axis and the total cost (including at least the integrated value of fuel costs and the cost of battery replacement) on the vertical axis.

[0065] The actual cost line 46 is the integrated value of fuel cost, i.e., a value calculated based on the historical fuel time series from purchase to the present and separately input fuel costs. The forecast line 48 from the present onwards is the predicted total cost if the battery continues to be used at the current battery degradation rate and fuel costs. The slope of this forecast line 48 is the same as the current slope of the actual cost line 46.

[0066] Next, the predicted line for the total cost if the battery is replaced now is predicted line 49. Here, the battery replacement cost 47 is taken into consideration. The current slope of predicted line 49 is the slope of current actual cost line 46 multiplied by 100 / SOHF. Prediction line 49 may be a straight line, or may be calculated based on past SOHF (a value that stores actual values ​​from when the battery was new to the present) (in which case it does not have to be a straight line).

[0067] Then, by comparing the values ​​of the forecast line 48 and the forecast line 49 in the year in which the series hybrid is scheduled to end operation, the user can determine whether or not to replace the battery in terms of cost.

[0068] This calculation and screen are based on the fuel economy of a series hybrid, but in reality, there is an SOHR where the battery resistance becomes too high and maximum power cannot be produced (for example, SOHR = 140 or SOHR = 200). In such cases, a separate warning message can be displayed on the screen stating that a battery replacement is required due to insufficient power. This guideline for SOHR can be calculated using the following conditions: {OCV (SOCL) x number of series - maximum allowable current x initial pack resistance x SOHR / 100} x maximum allowable current = required power, and {OCV (SOCL) - minimum voltage allowed for single cell} = maximum allowable current x initial single cell resistance x SOHR / 100.

[0069] Furthermore, when battery energy is used to start the engine, if only Es [kWh] is consumed from the battery, an additional charge of Es is required, and the engine-on time will be extended by ΔTs. The value of ΔTs is calculated by adding ΔTs = Es × 100 / {OCV(SOHL) × Qmax_present × number of series}, where OCV(SOHL) × Qmax_present × number of series}, where Qmax represents the battery's Ah capacity, and Qmax_present represents the current battery capacity.

[0070] As described above, the series hybrid according to the first embodiment calculates and outputs the fuel economy when the battery is replaced based on the battery resistance deterioration factor (SOHR_after / SOHR_before), the capacity deterioration factor (SOHQ_before / SOHQ_after), and engine on / off information.

[0071] This eliminates the influence of driving patterns and engine deterioration and provides information on the deterioration of fuel economy due only to battery deterioration, allowing the user to more accurately determine when to replace the battery.

[0072] [Example 2] In the case of railways, the motor load varies depending on the location, but the motor load does not change during a single operation. Therefore, it is preferable to set the time range of the information to be compiled as one operation. In other words, the compilation is performed after the end of the operation. It is also assumed that the load power P(t) of the train does not change during each operation. Therefore, engine on / off is determined based on the power time series.

[0073] In this flow, the charging power to the battery during charging is {Pg×S(t)-P(t)}×ηc, and the discharging power from the battery during discharging is -P(t)×ηd. When Pg×S(t)-P(t)>0, charging occurs, and when Pg×S(t)-P(t)<0, discharging occurs. S(t) is a function that represents the engine on / off information, and is 1 when on and 0 when off. Pg is the power generated by the generator when the engine is on.

[0074] The charge / discharge power Pb(t) to the battery is Pb(t) = {Pg × S(t) - P(t)} × η{Pg × S(t) - P(t)}, where the positive side is charging. η(x) is a function that is ηc when x>0, and ηd otherwise. For the battery, the engine is turned on when the stored energy falls below EL, and turned off when it rises above EH. EL is the stored energy of the battery when the SOC is SOCL, and EH is the stored energy of the battery when the SOC is SOCH.

[0075] Therefore, if S(t) = 1 and ∫Pb(t)dt≧Eh, then S(t+Δt) = 0, and if S(t) = 0 and ∫Pb(t)dt≦EL, then S(t+Δt) = 1. Otherwise, S(t+Δt) = S(t). Pg, ηc, ηd, SOHR, and SOHQ can be measured or found during this operation. The initial SOC0 of the battery is known or can be calculated.

[0076] For this reason, the initial battery energy after battery replacement is calculated by integrating OCV (SOC) from 0 to SOC0, dividing the result by 100 (essentially the average voltage from SOC0 to SOCL), multiplying it by the Ah capacity when the battery is new, and multiplying it by the number of batteries in series, to obtain E0_after. The initial value of S is set to 1. E_after(0) = E0_after. Then, for ηc and ηd, use the current values ​​to calculate the values ​​after battery replacement using equations 2 and 3.

[0077] E_after(t+Δt) is calculated as E_after(t)=E_after(t)+{Pg×S(t)-P(t)}×η(Pg×S(t)-P(t))×Δt, and S(t+Δt) is updated from E_after(t+Δt) (as mentioned above, S(t) determines whether it is 0 or 1). Then the time is updated as t=t+Δt. Note that "t=t+Δt" here refers to the program process of adding the increment Δt to the variable t. In this way, S(t) after the battery has been replaced is calculated.

[0078] The estimated fuel consumption after the battery replacement is calculated by adding μ × (the number of times S changed from 0 to 1 + 1) to the time integral of S(t) × f. This is the fuel (L or g) for one trip.

[0079] This flow is shown in Figure 5. This flow is executed by, for example, the ECU.

[0080] To summarize the above, in FIG. 5, ηc and ηd are first calculated (step S501), and E_after(0), Eh, and El are calculated (step S502). Eh and El may be predefined constants. Next, t and S(t) are initialized (step S503), and E_after(t+Δt) is calculated (step S504). If S(t)=1 and ∫Pb(t)dt≧Eh (step S505: YES), S(t+Δt)=0 is set (step S506). Otherwise (step S505: NO), the process proceeds to step S507. If S(t)=0 and ∫Pb(t)dt≦EL (step S507: YES), S(t+Δt)=1 is set (step S508). Otherwise (step S507: NO), the process proceeds to step S509. t=t+Δt is set (step S509). If t>operation time, the process ends (step S510: YES), otherwise (step S510: NO), the process returns to step S504.

[0081] Here, the charging efficiency and charge / discharge efficiency are not rigorous calculations but are approximations, and temperature changes are not taken into consideration. Therefore, the calculation in Figure 5 is a simple approximation. In reality, η depends on the current pattern. Therefore, it is also possible to perform a strict calculation as follows.

[0082] Since η depends on the current, it can also be calculated based on SOHR. To do this, find I(t) so that Pg×S(t)-P(t)=Pb(t)={OCV(SOC(t))+I(t)×R(SOC(t))×M(T(t))×SOHR / 100}×I(t). This is a quadratic equation for I. Two I values ​​are found, and the one with the smaller absolute value is selected as the solution. T(t) is a temperature time series, and this can also be estimated. It generates heat equal to "| I(t) × I(t) × R(SOC(t)) × M(T(t)) × SOHR / 100 | × number of series". Let this heat generation power be Ph(t).

[0083] Here, the temperature T(t + Δt) is calculated using the following formula using Newton's thermal model. Note that Newton's thermal model is just an example, and other models (such as a thermal circuit model) may also be used. Here, dT(t) / dt ≒ {T(t + ΔT) - T(t)} / ΔT, Ta is the outside air temperature, C is the heat capacity [J / K], α is the heat transfer coefficient, and S is the surface area [m 2 ] is a constant and is a value estimated and determined in advance. Ph(t) = M(T(t)) × {I(t) × r0(SOC(t)) × M(T(t)) × SOHR / 100 + vp1(t) + vp2(t)} × I(t) C × dT(t) / dt = {Ta - T(t)} × α × S + Ph(t) ... (Equation 10)

[0084] R(SOC) is a resistance table. It is preferable to prepare two R tables, one for the charge side and one for the discharge side at a specified temperature (e.g., 25°C) for a new battery. That is, when Pb(t) is negative, the discharge resistance table is used, and when Pb(t) is positive, the charge resistance table is used.

[0085] In the above equation, the resistance is pure resistance only, but in reality, the model is one in which several CR parallel circuits called polarizations are connected. An example of this is shown in Figure 6.

[0086] In the example of Figure 6, DC resistance r0, a CR parallel circuit consisting of DC resistance r1 and capacitor c1, and a CR parallel circuit consisting of DC resistance r2 and capacitor c2 are connected in series. Let the respective voltages be vp0(t), vp1(t), and vp2(t). Vp0(t) = r0 × I(t), and vp1(t) is expressed by the differential equation τ1 × dvp1(t) / dt + vp1(t) = I(t) × r1. From this, vp1(t + Δt) = vp1(t) + {I(t) × r1 - vp1(t)} × Δt / τ1 (τ1 = c1 × r1). In other words, the values ​​of vp1 and vp2 are known at time t.

[0087] From this, when polarization is two stages, the current I(t) is calculated using equation 11. Because it is a quadratic equation, there are two solutions, but the one with the smaller absolute value is used. Pb(t) = {OCV(SOC(t)+M(T(t))×(I(t)×r0(SOC(t))×M(t)×SOHR / 100+vp1(t)+vp2(t))}×I(t) ... (Equation 11)

[0088] Next, the temperature is updated using equation 10 based on I(t), and then the SOC is updated using equation 12, and vp1 and vp2 are updated using equation 13. Qmax_new represents the Ah capacity of a new battery. SOC(t+Δt) = SOC(t)+100×I(t)×Δt / {3600×Qmax_new×(SOHQ / 100)} ... (Equation 12)

[0089] vp1(t+Δt) = vp1(t)+{I(t)×r1×M(T(t))×SOHR / 100-vp1(t)}×Δt / τ1 vp2(t+Δt) = vp2(t)+{I(t)×r2×M(T(t))×SOHR / 100-vp2(t)}×Δt / τ2 … (Formula 13)

[0090] If the values ​​of r0, r1, and r2 differ between charging and discharging, the values ​​are determined by the sign of I(t) (or Pg×S(t)-P(t)). Specifically, if the sign of Pg×S(t)-P(t) is positive, the resistance on the charging side is used, and if it is negative, the resistance on the discharging side is used. Also, if the values ​​differ for each SOC, a table should be prepared.

[0091] M is a function that indicates how many times the resistance increases relative to the value at a predetermined temperature (for example, 25°C). A specific example of this function will be described in Example 3. If SOC is equal to or higher than SOCH and S(t) = 1, then S(t + Δt) = 0, and if SOC is equal to or lower than SOCL and S(t) = 0, then S(t + Δt) = 1. The above simulation is performed.

[0092] The above is summarized in Figure 7. This flow is executed by, for example, an ECU.

[0093] To summarize the above explanation, in FIG. 7, first, each variable is initialized (step S701), the current is calculated (step S702), the temperature is updated (step S703), the SOC is updated (step S704), and vp1 and vp2 are updated (step S705). If the SOC is equal to or greater than the SOCH and S(t)=1 (step S706: YES), S(t+Δt)=0 is set (step S707). If not (step S706: NO), the process proceeds to step S708. If the SOC is equal to or less than the SOCL and S(t)=0 (step S708: YES), S(t+Δt)=1 is set (step S709). If not (step S708: NO), the process proceeds to step S710. t=t+Δt is set (step S710). If t>operation time, the process ends (step S711: YES); if not (step S711: NO), the process returns to step S702.

[0094] As described above, the series hybrid according to the second embodiment calculates the current and voltage of the new battery based on the current battery voltage and temperature, the current battery current time series, the load current, the load voltage, the fuel efficiency time series, and the engine on / off information in the case where the current battery is replaced with a new battery to change the SOHR and SOHQ after the series hybrid has been operated.

[0095] Here, when calculating the current and voltage of a new battery, it is assumed that the load power given by load current x voltage remains unchanged. It is also assumed that the engine of a series hybrid system turns on when the battery reaches a predetermined lower limit of SOC or minimum stored energy, and turns off when the battery reaches a predetermined upper limit of SOC or maximum stored energy.

[0096] The series hybrid updates the battery SOC based on the current and voltage of a new battery, and calculates the engine on / off time series. The series hybrid also calculates fuel economy based on the engine on / off time series, fuel consumption when the engine is on, and excess fuel when the engine is on (not shown in FIG. 7, but this can be done in the same way as in Example 1).

[0097] This allows the fuel economy to be calculated taking into account the charging and discharging of the battery more appropriately.

[0098] Furthermore, the series hybrid according to the second embodiment calculates the discharge efficiency and charge efficiency, or calculates the battery voltage and current, based on a conversion value of how many times the battery resistance would increase if the battery temperature were a predetermined temperature (for example, 25°C), the battery temperature were the lowest temperature of the day, the battery temperature were the predicted average temperature of the day, the battery temperature were the predicted lowest temperature of the next day, or the battery temperature were the predicted average temperature of the next day.Then, the fuel economy is calculated and displayed based on the calculated discharge efficiency and charge efficiency, or based on the calculated voltage and current.

[0099] This allows the fuel consumption to be calculated taking temperature into more appropriate consideration.

[0100] After integrating P(t) over one trip, you can divide it by kWh to get L / kWh, or you can divide it by the duration of one trip to get L / h.

[0101] The screen may allow the user to select whether the aggregation unit is per cycle or per operation, as L / h, L / kWh, or L / operation.

[0102] It should be noted that this calculation may be carried out using the values ​​calculated in the simulation of the second embodiment, rather than the method described in the first embodiment.

[0103] [Example 3] In this example, temperature correction of SOHF is described. Battery temperature starts at a temperature roughly equivalent to the air temperature when the engine is started, and then rises due to Joule heat generated during charging and discharging. Therefore, initially, resistance is high and SOHF is large, but as the battery is used, resistance decreases and SOHF decreases. For this reason, it is useful to display the converted SOHF at a specified temperature.

[0104] Now, the charging power during charging is "{OCV + (V-OCV) × SOHR_after / SOHR_present} × current I". V-OCV is the value of resistance × current. If you know m(T), which indicates how many times the resistance is at a specific temperature (for example, 25°C) compared to the current temperature T°C, you can divide V-OCV by m(T) to get the voltage converted to the specific temperature (for example, 25°C). Therefore, the voltage is OCV + (V-OCV) × SOHR_after / {SOHR_present × m(T)}. This correction makes it possible to find ηc converted to the specific temperature (for example, 25°C).

[0105] Specifically, Ecg = ∫{V(t)-OCV(SOC(t))×I(t) / m(T(t))}dt, Et = ∫OCV(SOC(t))×I(t)dt, and the integration period is while the engine is on. Instead of Equation 2, Equation 14 holds. ηc = Et / (Et+Ecg*x) ... (Equation 14)

[0106] Similarly, ηd converted to a specified temperature (for example, 25°C) can be found. Therefore, SOHF converted to a specified temperature (for example, 25°C) can be calculated. Next, if the predicted temperature the next morning is Tp°C, you may want to display the converted SOHF at Tp°C. In this case, the voltage during charging is estimated as OCV + (V - OCV) × SOHR_after × M(Tp) / {SOHR_present × M(T)}. Then, ηc, ηd, and SOHF can be found.

[0107] When displayed, for example, "Tomorrow's temperature forecast is XXX°C. SOHF at tomorrow's YYY°C is ZZZ%." The temperature forecast is obtained, for example, from an external computer via the Internet. An example table of M(T) is shown in Figure 8. Here, a formula can be used instead of a table. The multiplication factor according to Arrhenius' law is written in formula 15. This B can be stored. The unit of T is [°C]. M(T) = exp[B / (T+273.15)-B(25+273.15)] ... (Formula 15)

[0108] [Example 4] In this example, server collaboration will be described. In server collaboration, the fuel efficiency of multiple vehicles is compared and preparations are made for batteries for maintenance. Alternatively, battery deterioration is predicted, the replacement time that will minimize costs is predicted, and a notification is sent to the user remotely.

[0109] An example of server linkage is shown in Figure 9. Series hybrid 91, server 92, and viewing terminal 93 are connected so that they can communicate with each other. Viewing terminal 93 is, for example, a terminal used by a user. Series hybrid 91 may not include server 92 and viewing terminal 93, or may include server 92 and viewing terminal 93. A series hybrid network including series hybrid 91, server 92, and viewing terminal 93 may be configured.

[0110] Here, information from the multiple series hybrids 91 is collected in a server 92. The information sent includes SOHF (converted at a predetermined temperature (e.g., 25°C)), estimated fuel consumption when the battery is replaced with a new one (which may also be converted at a predetermined temperature (e.g., 25°C)), BMU time series, ECU time series, etc.

[0111] Here, when the time series of the BMU and ECU are sent via communication, the server calculates the SOHF (converted to a predetermined temperature (for example, 25°C)). In addition, the data for the OCV table, the heat capacity of the temperature, and the constants of the resistance table may be transferred from the server to the series hybrid.

[0112] That is, the series hybrid according to Example 4 transmits from the server 92 to each series hybrid 91: - a function table showing the relationship between OCV and SOC or the relationship between resistance and SOC of the battery used in fuel consumption calculation; and - information showing the relationship between resistance and temperature.

[0113] This makes it easier to manage the function table and temperature information.

[0114] The estimated fuel economy when the battery is replaced with a new one depends on engine deterioration and driving patterns. Furthermore, if fuel economy in g / kWh or L / kWh is used, it will indicate engine deterioration that is not affected by driving patterns. Therefore, this fuel economy index may be considered an index of engine deterioration, and a warning may be issued for multiple series hybrids of the same model. The warning may be transmitted from server 92 to viewing terminal 93 and output on viewing terminal 93, for example.

[0115] In this way, in the series hybrid vehicle according to the fourth embodiment, the server 92 calculates the fuel efficiency. Alternatively, the server 92 receives the calculated fuel efficiency. Then, the server 92 notifies the user of the fuel efficiency. The notification is made, for example, via the viewing terminal 93.

[0116] This allows the user to easily check the fuel economy, which is convenient.

[0117] Furthermore, as shown in FIG. 9 , the series hybrid according to the fourth embodiment may: - calculate SOHF (State of Health for Fuel consumption) as an index showing fuel economy or engine deterioration for a plurality of series hybrids based on "volume of fuel consumed / energy used by the series hybrid system" or "weight of fuel consumed / energy used by the series hybrid system" converted at a predetermined temperature (for example, 25° C.); - compare the calculated fuel economy or SOHF; - notify the user of the series hybrid system with the most severe engine deterioration among the plurality of series hybrid systems.

[0118] This allows the user to make efficient decisions regarding multiple series hybrids.

[0119] Furthermore, by storing a time series of SOHF (e.g., converted to L / kWh at a given temperature (e.g., 25°C)) for multiple series hybrids, future SOHF predictions can be made. This makes it possible to predict the replacement timing that will minimize costs in the year the series hybrid is to be scrapped. An example of this screen is shown in Figure 10.

[0120] Figure 10 shows the time series of predicted total costs for a current SOHF when batteries are replaced at several different times. This time series was derived from past performance data for multiple batteries of the same type used in the same manner. When a battery is replaced, the total cost increases by the cost of the battery replacement (moving upwards vertically).

[0121] The cases where no replacement is made are shown with thick lines, with prediction line 1001 representing the case where replacement is made at the earliest first timing, prediction line 1002 representing the case where replacement is made at the second timing later than the first timing, prediction line 1003 representing the case where replacement is made at the third timing later than the second timing, and prediction line 1004 representing the case where replacement is made at the fourth timing later than the third timing.

[0122] 10, this means that the total cost in the planned disposal year will be minimized if the battery is replaced along prediction line 1003. Note that the prediction line may be a selection of past results that best match the usage of the battery being predicted, or a function that predicts the deterioration behavior of SOHR and SOHQ by functional approximation using temperature and SOC values.

[0123] The system then notifies the user of the timing for battery replacement that will minimize the total cost. At this time, the system (for example, the viewing terminal 93) may take into consideration the delivery time for the battery replacement and display a message such as "We recommend replacing the battery at XXX time."

[0124] In this way, the series hybrid according to the fourth embodiment predicts battery deterioration. Then, the total cost of battery replacement times over multiple days is calculated, and the replacement time that will minimize the total cost is predicted. The user may be notified of the replacement time. The series hybrid according to the fourth embodiment may also predict battery deterioration and, when the time for battery replacement is approaching, prompt the user to prepare a battery for maintenance. For example, an appropriate message may be output on the viewing terminal 93 a predetermined period before the replacement time that will minimize the total cost.

[0125] This increases convenience for the user.

[0126] The present invention is not limited to the above-described embodiments, but includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

[0127] Series hybrids include, but are not limited to, ships, railways, construction machinery, forestry machinery, agricultural machinery, and trams.

[0128] In the above examples, it is assumed that the battery is replaced with a new battery, but similar battery replacement determination is possible even when the battery is replaced with a used battery. In this case, the parameters after replacement can be set to values ​​corresponding to a used battery rather than a new battery, and as an example, SOHR_after is set to a value less than 100.

[0129] 41...Current fuel efficiency 42...Fuel efficiency when battery is replaced with a new one 43...Fuel efficiency deterioration rate SOHF due to battery deterioration 44...SOHR time series 45...Total cost time series 46...Actual cost line 47...Battery replacement cost 48...Prediction line 49...Prediction line 91...Series hybrid (series hybrid system) 92...Server 93...Viewing terminal 101...ECU (computer) 102...BMU 103...Fuel efficiency conversion unit 104...Engine (engine or fuel cell) 105...Generator 106...Battery pack 107...Drive motor 108...Hydraulic motor 1001...Prediction line 1002...Prediction line 1003...Prediction line 1004...Prediction line

Claims

1. A method for determining whether to replace a battery in a series hybrid system, characterized by calculating and outputting fuel efficiency when the battery is replaced based on the battery resistance deterioration factor, capacity deterioration factor, and engine or fuel cell on / off information.

2. A method for determining battery replacement in a series hybrid system according to claim 1, comprising: determining an on / off cycle of the engine or fuel cell in proportion to SOHQ; determining a deterioration in charging efficiency based on SOHR and extending the on-time of the engine or fuel cell; determining a deterioration in discharge efficiency based on SOHR and shortening the off-time of the engine or fuel cell; and calculating fuel economy using the above.

3. A method for determining battery replacement in a series hybrid system, in the case where the current battery is replaced with another battery after the series hybrid system has been operated, thereby changing the SOHR and SOHQ, calculating the current and voltage of the other battery based on the voltage and temperature of the current battery, the current time series of the current battery, the load current, the load voltage, the fuel efficiency time series, and on / off information of the engine or fuel cell of the series hybrid system, wherein when calculating the current and voltage of the other battery, it is assumed that the power of the load, given by the load current x voltage, does not change, and that the engine or fuel cell is turned on when the battery reaches a predetermined SOC lower limit or minimum stored energy, and turned off when the battery reaches a predetermined SOC upper limit or maximum stored energy, updating the SOC of the battery based on the current and voltage of the other battery, and determining the on / off time series of the engine or fuel cell, and determining fuel efficiency based on the on / off time series of the engine or fuel cell, the fuel consumed when on, and the extra fuel blown when the engine or fuel cell is turned on.

4. A method for determining battery replacement in a series hybrid system according to claim 1, characterized in that the SOHF (State of Health for Fuel consumption), an index of the impact of battery deterioration on fuel economy, is displayed as a ratio between the current fuel economy and the fuel economy that would result if the battery were replaced with another battery.

5. A method for determining whether to replace a battery in a series hybrid system according to claim 1, wherein the discharge efficiency and charge efficiency are calculated based on a conversion value of how many times the battery resistance would be if the battery temperature were to be a predetermined temperature, or if the battery temperature were the lowest temperature of the day, or if the battery temperature were the predicted average temperature of the day, or if the battery temperature were the predicted lowest temperature of the next day, or if the battery temperature were the predicted average temperature of the next day, or the battery temperature were the predicted average temperature of the next day, or the battery voltage and current are calculated based on said conversion value, and fuel economy is calculated and displayed based on the calculated discharge efficiency and charge efficiency, or based on the calculated voltage and current.

6. A method for determining whether to replace a battery in a series hybrid system as set forth in claim 1, characterized in that fuel efficiency is displayed in at least one of the following units: "volume of fuel consumed / hour," "volume of fuel consumed / energy used by the series hybrid system," "volume of fuel consumed / energy used in one operation," "mass of fuel consumed / hour," "mass of fuel consumed / energy used by the series hybrid system," or "mass of fuel consumed / energy used in one operation." 7. A method for determining whether to replace a battery in a series hybrid system according to claim 1, wherein a time series and predicted values ​​of total cost are presented, and wherein the total cost includes at least an accumulated value of fuel costs when the battery is replaced and a cost of replacing the battery.

8. The battery replacement determination method for a series hybrid system according to claim 1, wherein a server calculates the fuel efficiency, or the server receives the calculated fuel efficiency, and the server notifies the user of the fuel efficiency.

9. A method for determining battery replacement in a series hybrid system according to claim 8, comprising: calculating SOHF (State of Health for Fuel consumption) as an index showing fuel economy or engine or fuel cell deterioration for a plurality of series hybrid systems based on "volume of fuel consumed / energy used by the series hybrid system" or "weight of fuel consumed / energy used by the series hybrid system" converted at a predetermined temperature; comparing the calculated fuel economy or SOHF; and notifying the series hybrid system with the most severe engine or fuel cell deterioration among the plurality of series hybrid systems.

10. A battery replacement determination method for a series hybrid system according to claim 8, characterized in that it predicts battery deterioration, calculates the total cost of battery replacement over multiple days, and predicts the replacement time when the total cost will be minimized, or calculates the total cost of battery replacement over multiple days, and predicts the replacement time when the total cost will be minimized, and notifies the user of the replacement time, or prompts the user to prepare a battery for maintenance when the time for battery replacement is approaching.

11. A method for determining whether a battery needs to be replaced in a series hybrid system according to claim 8, wherein a function table showing the relationship between OCV and SOC or the relationship between resistance and SOC of a battery used in fuel economy calculations, and information showing the relationship between resistance and temperature are transmitted from a server to each series hybrid system.

12. A method for determining whether a battery should be replaced in a series hybrid system, comprising the steps of calculating and outputting fuel efficiency in the event of battery replacement based on the resistance deterioration factor, capacity deterioration factor, and on / off information of the engine or fuel cell in the series hybrid system.

13. A recording medium having recorded thereon a program that causes a computer that controls a series hybrid system to calculate and output fuel efficiency when the battery is replaced based on the battery resistance deterioration rate, capacity deterioration rate, and on / off information of the engine or fuel cell.

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